1. Field of the Invention
The present invention relates to a cylinder cleaning mechanism for cleaning a cylinder of a printing press.
2. Description of the Prior Art
A printing press, such as a sheet-fed printing press or a rotary printing press, is provided with a cylinder cleaning mechanism having a cylinder cleaning unit employing a cleaning cloth for cleaning the circumference of the cylinder between successive printing cycles to prevent smearing printing sheets with an ink adhering to the circumference of the impression cylinder or the blanket cylinder. The cleaning cloth is wound at a predetermined rate so that a new portion of the cleaning cloth is pressed always against the circumference of the cylinder so that the circumference of the cylinder can perfectly be cleaned.
A conventional cylinder cleaning mechanism for cleaning the impression cylinder of a printing press will be described with reference to FIG. 7 to 11. There are shown a cylinder cleaning unit 8, side plates 2, an intermediate cylinder 3, an impression cylinder 4 to be cleaned by the cylinder cleaning unit 8, a recess 4a formed in the circumference of the impression cylinder 4, gripping fingers 6a, a gripper shaft 6b fixedly holding the gripping fingers 6a and capable of rocking to hold the edge of a printing sheet on a portion of the circumference of the impression cylinder 4 near the front edge 4b of the recess 4a with the gripping fingers 6a, a cleaning cloth 20, a pressure blade 10 having a front frame 10a and a rear frame 10b, for pressing the cleaning cloth 20 through a pressure pad 12 against the circumference of the impression cylinder 4, a cleaning cloth feed roller 14, a cleaning cloth winding roller 16, a guide bar 18 for guiding the cleaning cloth 20, a main frame 22 of the printing press, a rotary shaft 24 supporting the cylinder cleaning unit 8, bearings supporting the rotary shaft 24 for rotation on the main frame 22, a lever 26 attached to a rotary shaft 36 supported on bearings 36b to turn the cylinder cleaning unit 8 on the rotary shaft 24, a cam roller 30 supported on the lever 26 by a pin 28, a cam 50 engaging the cam roller 30 to turn the lever 26 in synchronism with the motion of the gripping fingers 6a, fixed to the intermediate cylinder 3 with bolts 52 and having a high cam section 50a and a low cam section 50b, a link 34 having one end joined to the lever 26 by a pin 32 and the other end joined to the side plate 2 of the cylinder cleaning unit 8 by a pin 38, a compression spring 40 having one end 44 joined to one end of the lever 26 by a pin 48 and the other end contiguous with a spring seal 46 mounted on a rod 42 to compress the compression spring 40, and a pneumatic actuator 74 having one end fixed with a bolt 84 to a bracket 86 fixed to the main frame 22 and the other end connected to the lever 26 to shift the cylinder cleaning unit 8 between a cleaning position and an escape position.
The pneumatic actuator 74 has a piston rod 76, and a connecting member 78 attached to the extremity of the piston rod 76 and provided with a slot 80 receiving a pin 82 fixed to the lever 26 therein to allow the lever 26 to swing so that the lever 26 may not interfere with the gripping fingers 6a. The cylinder cleaning unit 8 is retracted from its cleaning position to avoid the interference of the cylinder cleaning unit 8 with the gripping fingers 6a, and then the cylinder cleaning unit 8 is returned to its cleaning position after the gripping fingers 6a have passed a position corresponding to the cleaning position. A gear 58 is mounted on a one-way clutch 60 attached to one end of the shaft of the cleaning cloth winding roller 16, and a segment gear 62 is fixed to the main frame 22 with bolts 64 and 66 so as to engage the gear 58. Every time the cylinder cleaning unit 8 is turned on the rotary shaft 24 between the cleaning position and the escape position, the gear 58 rolls along the segment gear 62 to turn the cleaning cloth winding roller 16 through the one-way clutch 60 in one direction to wind up the cleaning cloth 20 by a predetermined length.
The operation of the cylinder cleaning unit 8 will be described hereinafter. Referring to FIG. 7 showing a state in which the recess 4a of the impression cylinder 4 has almost arrived at a position directly below the pressure blade 10, the cam roller 30 attached to one end of the lever 26 is on the low cam section 50b of the cam 50 and hence the cylinder cleaning unit 8 is at the cleaning position with the center of the cleaning cloth winding roller 16 at a position A. In this state, the cleaning cloth 20 is pressed against the circumference of the impression cylinder 4 through the pressure pad 12 by the pressure blade 10 to clean the circumference of the impression cylinder 4.
Upon the arrival of the front edge of the recess 4a at the position directly below the pressure blade 10, the cam roller 30 engages the high cam section 50a of the cam 50 to withdraw the cylinder cleaning unit 8 from the cleaning position and, consequently, the lever 26 is turned clockwise to turn the cylinder cleaning unit 8 on the rotary shaft 24 in a counterclockwise direction through the link 34, so that the center of the cleaning cloth winding roller 16 is shifted to a position B as shown in FIG. 8. While the center of the cleaning cloth winding roller 16 is being shifted from the position A to the position B, the gear 58 engaging the segment gear 62 is rotated clockwise. The rotation of the gear 58 is transmitted through the one-way clutch 60 to the cleaning cloth winding roller 16 to wind up the cleaning cloth 20 by a predetermined length. While the cylinder cleaning unit 8 is being withdrawn from the cleaning position, the pin 82 attached to the lever 26 is able to move in the slot 80 of the connecting member 78 and, therefore, the withdrawal of the cylinder cleaning unit 8 from the cleaning position to avoid the interference of the cylinder cleaning unit 8 with the gripping fingers 6a and the advancement of the cylinder cleaning unit 8 to the cleaning position are not obstructed at all by the pneumatic actuator 74.
As the intermediate cylinder 3 and the impression cylinder 4 rotate further from the position shown in FIG. 8 and the high cam section 50a of the cam 50 passes the cam roller 30, the lever 26 is turned counterclockwise by the compression spring 40 to turn the cylinder cleaning unit 8 clockwise on the rotary shaft 24 to the cleaning position, in which the center of the cleaning cloth winding roller 16 is located at the point A. Although the gear 58 engaging the segment gear 62 is rotated counterclockwise while the cylinder cleaning unit 8 is being turned clockwise, the counterclockwise rotation of the gear 58 is not transmitted to the cleaning cloth winding roller 16. Thus, the cleaning cloth 20 is wound by the predetermined length once every printing cycle, so that the circumference of the impression cylinder 4 is cleaned always with a new portion of the cleaning cloth 20.
After the completion of the cleaning operation or in replacing the used cleaning cloth with a new one, the lever 26 is turned clockwise against the pressure of the compression spring 40 by the pneumatic actuator 74 to turn the cylinder cleaning unit 8 counterclockwise on the rotary shaft 24 beyond the escape position to a standby position, in which the center of the cleaning cloth winding roller 16 is at a point C as shown in FIG. 9.
After the used cleaning cloth 20 has been replaced with a new one or when the cleaning operation is required again, the piston rod 76 of the pneumatic actuator 74 is retracted to allow the lever 26 to be turned counterclockwise by the pressure of the compression spring 40 to shift the cylinder cleaning unit 8 from the standby position to the cleaning position as shown in FIG. 7.
Since the pressure of the compression spring 40 pressing the pressure blade 10 through the cleaning cloth 20 against the circumference of the impression cylinder 4 is not adjustable, in some cases, the cleaning cloth 20 cannot be pressed against the circumference of the impression cylinder 4 at an appropriate pressure and hence the circumference of the impression cylinder 4 cannot perfectly be cleaned. The employment of the compression spring 40 and the pneumatic actuator 74 respectively for pressing the pressure blade 10 against the circumference of the impression cylinder 4 and turning the cylinder cleaning unit 8 to the standby position increases the number of component parts and needs additional space for those components.